<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<style>
article{
    width: 500px;
    height: 500px;
    border: 2px solid springgreen;
    margin: auto;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;


}

</style>
<body>
    <article>

    </article>
    
</body>
</html>